In testing electrical components having a plurality of leads, the leads are frequently inserted into socket-type contacts which are coupled to an associated test circuit. Socket-type contacts typically include spaced contact fingers which provide a resilient opening into which the leads are inserted. Ideally, the resiliency of the fingers insures proper electrical contact between the leads and the test circuit. However, due to constant use, the resiliency of the contact fingers is reduced. Moreover, the leads are coated typically with solder which results in a larger and nonuniform size of the leads. Thereafter, when the solder coated leads are inserted into the socket-type contacts, the contacts tend to (1) wear rapidly, (2) lose their resiliency and (3) permanently separate to a position where proper electrical contact is no longer insured. Additionally, as the leads of successive components are inserted into the socket-type contacts, the contacts tend to make electrical engagement with the leads at different points on the leads thus introducing a variable into the testing process. This is particularly undesirable where sensitive electrical parameters, such as the insertion loss of 100 MHz pulse transformers, are being measured. In addition, as the socket-type contacts wear and have to be replaced, the testing system must be recalibrated. Similarly, the conductors connecting the socket-type contacts to the test circuit also tend to introduce undesirable variables into the testing system.
In an attempt to overcome the above-mentioned disadvantages, the use of zero-insertion force test contacts have been used. One known fixture, which facilitates the testing of amplifiers and which utilizes zero-insertion force test contacts, includes a plurality of lead-receiving slots. A test contact is positioned adjacent one end of each of the plurality of slots. A spring biased plunger is positioned adjacent an opposite end of each of the plurality of slots. To insert the leads of the amplifier the plungers are moved in a direction away from the test contacts. The leads are then inserted into the slots and the plungers are released so that the biasing action of each of the plungers forces the associated leads into one of the test contacts. Capacitors, which are coupled to an opposite end of the test contacts, are connected to a test set through electrical jacks. While this fixture helps reduce damage to the leads and to reduce wear on the test contacts, the fixture is still susceptible to the introduction of undesirable variables into the testing system.
Accordingly, a purpose of this invention is to provide a method and fixture for establishing an electrical connection to a circuit which avoids the introduction of undersirable variables into the testing system.